The ESI Solution: High-Throughput Roll-to-Roll UV Laser Drilling of Thin, Flex Materials

Estimated reading time: 7 minutes

Riechel: It's still very common to have 100 micron vias. However, as consumer electronics keeps getting smaller and the via densities get tighter, the line and space widths are shrinking and our customers are moving to smaller and smaller via sizes. A 50 micron via is not so uncommon anymore. We do have customers that are processing down to 30 micron through-vias, but I would say that was still at the relative leading edge of mass production. Some of our customers are processing down to 20 micron through-vias, but that is typically at a much more limited volume. That probably gives you a good overview.

Starkey: What is the laser technology that you're using?

Riechel: We have historically used UV nanosecond lasers, but as we've expanded our laser portfolio we are moving from not just diode-pumped UV lasers, but to fiber laser technologies such as on our GemStone product.

Starkey: Your laser will cut clean through copper-Kapton-copper, straight through the three layers?

Riechel: We can perform this type of through-cut processing, as well as blind-via processing on very thin materials, which is one of many areas that we believe ESI’s flex processing product portfolio excels at. It's very important to have excellent power control and also control other factors related to what we call laser fluence. Laser fluence is the laser energy per area that you're drilling on. To have very good control of that fluence is critical to not overdosing a specific area of material and cutting too far through your blind-via area. So for a blind via to stop in that second layer of copper, and not damage the material, you have to have very good control of the laser fluence. We do that very well. We also do through-vias, through copper-Kapton-copper. In some cases, in multilayer constructions, we are cutting through not just the copper-Kapton-copper, but adhesive materials as well. And in some situations we're cutting through four or five layers of copper.

Starkey: Would this be flex multilayer or flex-rigid multilayer?

Riechel: Typically, it's flex multilayer but we do have customers that are also cutting or drilling flex-rigid constructions.

Starkey: Glass reinforcement would present no problems to the system?

Riechel: The challenge of glass reinforcement with UV drilling is that, unlike CO₂ processing where the CO₂ wavelength is reflected by the copper layer, you can cut through copper with UV pretty readily. With glass-reinforced materials, the glass fibers have a very similar ablation threshold to copper. Typically, if it’s a flex-rigid construction, customers will use their UV drills for through-via processes, because it's significantly more challenging to develop a technique that cuts cleanly through the glass material and stops in the bottom layer of copper.

Starkey: How do you see the market moving in China? What is the next generation going to be demanding of you, as suppliers of precision machining technology?

Riechel: Good question. We're really excited about the China market. That's one reason that we're here at CPCA and HKPCA as well. The China market is continually growing. The China manufacturers are becoming increasingly sophisticated as well. Where maybe 10 years ago the majority of the drilling market might have been in CO₂ drilling and mechanical drilling, the same manufacturers are now progressing into the smaller via drills that require UV laser drilling.

As a result, we're seeing that our own market is expanding. Furthermore, you're no longer just seeing that customer base in the typical manufacturing hubs in Suzhou, Kunshan and Shenzhen. We're seeing more and more expansion into other areas of China. That is one reason that we have decided to partner with WKK, as they have an extremely good network of sales representatives throughout China. We feel that it's critical to have that network to truly do justice to serving the customer base in these other areas of China.

Starkey: How many installations do you have in China?

Riechel: For  all ESI tools, certainly over 1,000. For UV laser drilling tools for flex processing, I would say somewhere between 500 and 600.

Starkey: Thank you very much indeed for spending your time. That's been a very interesting conversation.

Riechel: It has been my pleasure, Pete.

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